The present invention relates to a rotating shaft apparatus for driving a spindle to which a tool or a workpiece is mounted or for driving feed screw shafts provided in X-, Y- and Z-orthogonal three axes, and a machine tool such as a milling machine, a machining center, a grinding machine, a lathe, an electric discharge machine. The invention relates to a novel technique which enhances the durability if the rotating shaft, such as a spindle or a feed shaft rotates at a high rotational speed.
In rotating shaft apparatuses having a spindle or feed shafts of a machine tool, bearings, for rotationally supporting the shaft, generate a heat due to the rotation of the rotating shaft. The heat is transmitted to the rotating shaft to increase the temperature of the rotating shaft, which results in a thermal deformation thereof. For example, a spindle apparatus which rotates at a high speed exhibits remarkably such a trend. Therefore, a liquid coolant for cooling the spindle and preventing the increase in the temperature thereof and a lubrication for the bearings for supporting the spindle are required to be effective and optimum. On the other hand, increase in feeding speed of the X-, Y- and Z-orthogonal three axes is also desired. Therefore, as in case of the spindle, a liquid coolant for cooling the feed shafts and preventing the increase in the temperature thereof and a lubrication for the bearings for supporting the feed shafts are required to be effective and optimum. In such a field of the art, there are the following prior art.
As a first prior art, Japanese Unexamined Patent Publication (Kokai) No. 63-62638 discloses lubricating apparatus for a machine tool having a vertical spindle. The apparatus executes a jet lubrication in which a lubricating oil in the form of a jet is directed to a rolling member provided between inner and outer races of a bearing for rotationally supporting a spindle through a lubricating oil supplying nozzle provided adjacent the bearing, the lubricating oil being supplied to the nozzle from a lubricating oil supplying apparatus provided outside of the spindle apparatus through a lubricating oil supplying conduit.
As a second prior art, Japanese Unexamined Patent Publication (Kokai) No. 61-16252 discloses a bearing lubricating apparatus. The apparatus executes an oil air lubrication in which a lubricating oil in the form of an aerosol is directed to a rolling member provided between inner and outer races of a bearing for rotationally supporting a spindle through a lubricating oil supplying pipe provided adjacent the bearing, the lubricating oil being supplied to the lubricating oil supplying pipe from a lubricating oil supplying apparatus provided outside of the spindle apparatus through a lubricating oil supplying conduit.
As a third prior art, Japanese Patent Publication No. 2541700 discloses a bearing lubricating apparatus. The apparatus executes an under-race lubrication in which a lubricating oil is directed, by centrifugal force due to the rotation of a spindle, to a rolling member provided between inner and outer races of a bearing through a passage provided in the inner race of the bearing, the lubricating oil being supplied to a lubricating oil supplying passage provided in the spindle along the axis thereof from a lubricating oil supplying apparatus provided outside of the spindle apparatus.
As a fourth prior art, Japanese Unexamined Patent Publication (Kokai) No. 4-57355 discloses a spindle apparatus. The apparatus executes another type under-race lubrication by a configuration different from the third prior art. The lubricating oil is directed, by centrifugal force due to the rotation of a spindle, to a rolling member provided between inner and outer races of a bearing through a passage provided in the inner race of the bearing, the lubricating oil being supplied to a lubricating oil supplying passage provided in a drawbar, inserted in the spindle for drawing a tool to the spindle, from a lubricating oil supplying apparatus provided outside of the spindle apparatus.
AS a fifth prior art, Japanese Unexamined Patent Publication (Kokai) No. 64-87130 discloses a spindle apparatus in which a liquid coolant flows through a spindle. The liquid coolant is supplied into a space, between a cavity formed in the spindle and a drawbar provided in the cavity, from a coolant source provided outside of the spindle apparatus to cool the spindle from its inside. The bearings for rotationally supporting is indirectly cooled by the liquid coolant.
As a sixth prior art, Japanese Publication No. 2677505 discloses a spindle apparatus. In this apparatus, a liquid lubricant is supplied into a space, between a cavity formed in the spindle and a drawbar provided in the cavity, or into a drawbar provided in the spindle for holding a tool to the spindle, from a lubricant source provided outside of the spindle apparatus to cool the spindle from its inside. Further, the lubricant is supplied, by the centrifugal force due to the rotation of the spindle, to the rolling members provided between inner and outer races of a bearing for rotationally supporting the spindle through a passage of the inner race to execute a under-race lubrication. The lubricant is further supplied to the housing to cool indirectly the outer race of the bearing and a built-in motor, thereafter the lubricant is recovered.
AS a seventh prior art, Japanese Unexamined Patent Publication (Kokai) No. 8-118199 discloses a feeding apparatus for a machine tool. In this apparatus, a liquid coolant is supplied into a cavity provided in a feed screw shaft from a coolant temperature adjusting apparatus provided outside of the feeding apparatus to cool the feed screw shaft from its inside. Further, the coolant is supplied, by centrifugal force generated by the rotation of the feed screw shaft, to the rolling members provided between inner and outer races of a bearing for rotationally supporting the feed screw shaft through a passage of the inner race to execute a under-race lubrication, thereafter the coolant is recovered.
In the jet lubrication of the first prior art, the liquid lubricant in the form of a jet is directed to the rolling member provided between the inner and outer races through a lubricant supplying nozzle. Therefore, special nozzle and liquid lubricant supply passage is required, which makes the configuration of the spindle apparatus complex. Further, since the liquid lubricant is supplied through a long lubricant supply passage, the liquid lubricant may be contaminated by a foreign particles, such as a dust so that the spindle is rapidly damaged by the foreign particles when the spindle rotates, in particular at a high rotational speed.
In the oil air lubrication of the second prior art, the liquid lubricant in the form of an aerosol is directed to the rolling member provided between the inner and outer races through the lubricating oil supplying nozzle. Therefore, as in the first prior art, special nozzle and liquid lubricant supply passage is required, which makes the configuration of the spindle apparatus complex. Further, since the liquid lubricant is supplied through a long lubricant supply passage, the liquid lubricant may be contaminated by a foreign particles, such as a dust so that the spindle is rapidly damaged by the foreign particles when the spindle rotates, in particular at a high rotational speed.
In the under-race lubrication of the third prior art, the liquid lubricant is supplied to the rolling member provided between the inner and outer races through the passage provided in the inner race by the centrifugal force due to the rotation of a spindle. According to the under-race lubricant, when the spindle rotates at a high rotational speed, for example above 20000 minxe2x88x921, it is difficult to control the flow rate of the liquid lubricant supplied to the bearing by the effect of the centrifugal force due to the rotation of the spindle, and in some case, the increase in the amount of the lubricant supplied to the bearing results in the increase in the heat generated by the shearing force between the rolling member and the liquid lubricant. Further, since the liquid lubricant is supplied to the lubricant supplying passage provided in the spindle from the lubricating oil supplying apparatus provided outside of the spindle apparatus, the liquid lubricant flowing through a long lubricant supply passage system may be contaminated by a foreign particles, such as a dust existing in the system so that the passage between the lubricant supplying passage in the spindle and the bearing is blocked by the foreign particles, and the spindle is rapidly damaged by insufficient lubrication.
Although the under-race lubrication of the fourth prior art is different from that of the third prior art, the fourth prior art has a problem the same as the third prior art that the passage between the lubricant supplying passage in the spindle and the bearing is blocked by the foreign particles.
In the sixth prior art, a core cooling is executed in which the liquid lubricant for the bearing is supplied into the cavity formed in the spindle from the lubricant source provided outside of the spindle apparatus to cool the spindle from its inside. Thereafter, the lubricant is supplied, by the centrifugal force due to the rotation of the spindle, to the rolling members provided between inner and outer races of the bearing for rotationally supporting the spindle through a passage of the inner race to execute a under-race lubrication. The lubricant is further supplied to the housing to cool indirectly the outer race of the bearing and the built-in motor, thereafter the lubricant is recovered. Cooling of a spindle and lubrication for a bearing is essentially different from each other. Therefore, when the spindle is cooled by a lubricant for a bearing, it is not possible to optimize both the cooling of the spindle and the lubrication for the bearing. Further, in the configuration that the liquid lubricant for dual-purpose of lubrication and cooling is supplied to the cavity of the spindle from the liquid lubricant supplying apparatus provided outside of the spindle and the liquid lubricant outcome from the spindle is recovered to the lubricant source, the liquid lubricant may be contaminated by a foreign particles, such as a dust so that the spindle is rapidly damaged by the foreign particles when the spindle rotates, in particular at a high rotational speed.
In the under-race lubrication of the seventh prior art, the liquid coolant is supplied into the cavity provided in a feed screw shaft from the coolant temperature adjusting apparatus provided outside of the feeding apparatus to cool the feed screw shaft from its inside, then the coolant is supplied, by centrifugal force generated by the rotation of the feed screw shaft, to the rolling members provided between inner and outer races of a bearing from the cavity of the spindle. In the seventh prior art, as in the sixth prior art, the feed screw shaft is cooled by the lubricant for the bearing. Therefore, there are problems that it is not possible to optimize both the cooling of the spindle and the lubrication of the bearing, and the spindle is rapidly damaged by the foreign particles involved in the liquid lubricant.
The invention is directed to solve the above-described problems, and the objection of the invention is to provide a rotating shaft apparatus and a machine tool having the rotating shaft apparatus, which apparatus is enhanced its durability if the rotating shaft rotates at a high rotational speed.
Further, the objective of the invention is to provide a rotating shaft apparatus and a machine tool having the rotating shaft apparatus having a relatively simple configuration. The apparatus allows a lubricant to be supplied to the bearing at an optimized flow rate if the rotating shaft rotates at a high rotational speed.
Further, the objective of the invention is to provide a rotating shaft apparatus and a machine tool having the rotating shaft apparatus, which apparatus improved to prevent contamination in the lubricant.
Further, the objective of the invention is to provide a rotating shaft apparatus and a machine tool having the rotating shaft apparatus, which apparatus improved to optimize the cooling of the spindle and the lubrication for the bearing.
Further, the objective of the invention is to provide a rotating shaft apparatus and a machine tool having the rotating shaft apparatus, which apparatus improved to effectively cool the spindle as well as to prevent contamination in the lubricant.
In order to achieve the above-described objectives, according to the invention, a rotating shaft is rotationally supported by a bearing to a housing, the bearing being previously applied to or filled with a lubricant. A lubricant impregnated member, which is impregnated with a lubricant to be supplied to the bearing, is provided in the rotating shaft. The lubricant is separated and discharged from the lubricant impregnated member by centrifugal force due to the rotation of the shaft. The lubricant is supplied to the bearing through a lubricant supplying passage which is provided for fluidly connecting a space in or adjacent the bearing and the lubricant impregnated member.
According to the invention, there is provided a rotating shaft apparatus for driving a shaft rotationally supported by a housing, comprising a bearing for rotationally supporting the shaft in the housing, the bearing being previously applied to or filled with a lubricant; a lubricant impregnated member, which is impregnated with a lubricant to be supplied to the bearing and provided in the rotating shaft, the lubricant being separating and discharging the lubricant by centrifugal force due to the rotation of the shaft; and a lubricant supplying passage for fluidly connecting a space in or adjacent the bearing and the lubricant impregnated member to supply the lubricant which has been separated and discharged from the lubricant impregnated member.
According to the invention, a rotating shaft is rotationally supported to a housing by a bearing previously applied to or filled with a lubricant, and mounted in the rotating shaft is a lubricant impregnated member, which is impregnated with a lubricant to be supplied to the bearing so that the lubricant is separated and discharged from the lubricant impregnated member by centrifugal force due to the rotation of the shaft and supplied to the bearing through the lubricant supplying passage for fluidly connecting a space in or adjacent the bearing to the lubricant impregnated member. Therefore, the energy of centrifugal force due to the rotation of the shaft is consumed so that the excessive supply of the lubricant is prevented. The lubricant is supplied to the bearing only from the lubricant impregnated member which is mounted to the rotating shaft. Therefore, the lubricant for the bearing is not contaminated.
Providing a lubricant previously applied to or filled in the bearing prevents insufficient lubrication when the rotating shaft apparatus is activated first after the rotating shaft is assembled to the apparatus. The lubricant may include a grease or a base oil.
The lubricant impregnated member includes a permeable material or a non-woven material to which the lubricant is impregnated. In particular, the lubricant impregnated member may include a permeable member, for example a permeable polymeric material such as polyethylene, into which a liquid lubricant. Thereafter, the lubricant impregnated member is shaped into a bar by applying a heat. A microporous membrane member may be applied to the outer surface of the lubricant impregnated member.
Adjustment means for adjusting the rate of the lubricant supplied to the bearing from the lubricant impregnated member may be provided. The adjustment means may comprise an orifice provided in the lubricant supplying passage. Provision of the adjustment means allows optimization of the flow rate of the lubricant to prevent an excessive supply of the lubricant, which extends the life time of the lubricant impregnated member and prevents an excessive heat generation in the bearing.
Further, core cooling means may be provided in the shaft which means includes passages for supplying liquid coolant to the core portion of the rotating shaft from a coolant supplying and circulating apparatus, and for recovering the liquid coolant used for cooling the rotating shaft. In this case, the lubricant is supplied to the bearing only from the lubricant impregnated member which is mounted to the rotating shaft, and the lubrication for the bearing and the cooling of the rotating shaft can be independently carried out. Therefore, an optimized lubricant for the bearing and liquid coolant can be selected and supplied to the bearing and the shaft at optimized flow rates.
According to another feature of the invention, there is provided a machine tool for machining a workpiece by relatively moving a tool and the workplace to each other, comprising a table for mounting the workpiece; a feed mechanism for driving X-, Y- and Z-feed shafts for relatively moving a spindle to which the tool is mounted and the table to each other; a spindle to which the tool is mounted and is rotationally supported by a spindle head; a bearing for rotationally supporting the spindle to the spindle head; a lubricant impregnated member, which is impregnated with a lubricant to be supplied to the bearing and provided in the rotating shaft, for separating and discharging the lubricant by centrifugal force due to the rotation of the shaft; and a lubricant supplying passage for fluidly connecting a space in or adjacent the bearing and the lubricant impregnated member to supply the lubricant which has been separated and discharged from the lubricant impregnated member.
According to the invention, a lubricant impregnated member, which is impregnated with a lubricant to be supplied to the bearing, is mounted in the spindle of a machine tool, which holds a tool and is rotationally supported to a spindle head by a bearing, so that the lubricant is separated and discharged from the lubricant impregnated member by centrifugal force due to the rotation of the spindle and supplied to the bearing through the lubricant supplying passage for fluidly connecting a space in or adjacent the bearing and the lubricant impregnated member. Therefore, the lubricant for the bearing is not contaminated.
Further, core cooling means may be provided in the spindle which means includes passages for supplying liquid coolant to the core portion of the spindle from a coolant supplying and circulating apparatus, and for recovering the liquid coolant used for cooling the rotating shaft. In this case, the lubricant is supplied to the bearing only from the lubricant impregnated member which is mounted in the spindle, and the lubrication for the bearing and the cooling of the rotating shaft can be independently carried out. Therefore, an optimized lubricant for the bearing and liquid coolant can be selected and supplied to the bearing and the shaft at optimized flow rates.
According to another feature of the invention, there is provided a machine tool for machining a workpiece by relatively moving a tool and the workpiece to each other, comprising a feed mechanism for driving X-, Y- and Z-feed shafts for relatively moving the spindle and a table to each other; a bearing for rotationally supporting the feed screw shaft of the feed mechanism; a lubricant impregnated member, which is impregnated with a lubricant to be supplied to the bearing and provided in the feed screw shaft, for separating and discharging the lubricant by centrifugal force due to the rotation of the shafts and a lubricant supplying passage for fluidly connecting a space in or adjacent the bearing and the lubricant impregnated member to supply the lubricant which has been separated and discharged from the lubricant impregnated member.
According to the invention, a lubricant impregnated member, which is impregnated with a lubricant to be supplied to the bearing, is mounted in the feed screw shaft of a machine tool which is rotationally supported by a bearing, so that the lubricant is separated and discharged from the lubricant impregnated member by centrifugal force due to the rotation of the screw shaft and supplied to the bearing through the lubricant supplying passage for fluidly connecting a space in or adjacent the bearing and the lubricant impregnated member. Therefore, the lubricant for the bearing is not contaminated.
According to the above-described features of the invention, there is provided a machine tool having a rotating shaft apparatus in which the durability is enhanced if the rotating shaft, such as the spindle or the feed screw shaft rotates at a high speed.
A relatively simple configuration in which a lubricant impregnated member, which is impregnated with a lubricant to be supplied to the bearing, is provided in a rotating shaft, such as a spindle or a feed screw shaft, allows optimized and minimized amount of lubricant to be supplied to the bearing. Therefore, excessive heat generation due to excessive supply of the lubricant is prevented.
The lubricant is supplied to the bearing from the lubricant impregnated member which is mounted in the rotating shaft such as a spindle or a feed screw shaft through a lubricant supplying passage. Therefore, the lubricant supplied to the bearing is not contaminated by foreign particles such as a dust and the excessive heat generation is prevented so that a clean and durable rotating shaft apparatus is realized.
If core cooling means is provided in the shaft, which means includes passages for supplying liquid coolant to the core portion of the rotating shaft from a coolant supplying and circulating apparatus, and for recovering the liquid coolant used for cooling the rotating shaft, the lubricant is supplied to the bearing only from the lubricant impregnated member which is mounted to the rotating shaft, and the lubrication for the bearing and the cooling of the rotating shaft can be independently carried out. Therefore, an optimized lubricant for the bearing and liquid coolant can be selected and supplied to the bearing and the shaft at optimized flow rates.
In the first and second prior art, the liquid lubricant is directed from the lubricant supplying apparatus, provided outside of the spindle apparatus, to the rolling member provided between inner and outer races through the lubricant supplying nozzle. On the other hand, in the invention, the lubricant is supplied from the lubricant impregnated member to a bearing through the lubricant supplying passage. Therefore, the lubricant is not contaminated by foreign particles such as a dust so that the rapid wear of the bearing is prevented. Further, the lubricant does not seep out of the lubricant impregnated member if it is employed to a spindle or a feed screw shaft which rotates about a vertical axis.
The under-race lubrication of the third and fourth prior art has problems that the lubricant may be excessively supplied to the bearing by the effect of centrifugal force due to the rotation of the spindle and that the lubricant is contaminated by foreign particles such as a dust. On the other hand, the invention is not involved such problems.
The fifth prior art is merely a spindle core cooling. On the other hand, the invention employs a novel configuration in that the lubricant is supplied to the bearing from the lubricant impregnated member to optimize the lubrication of the bearing and to prevent the heat generation in the spindle and the bearing.
The sixth and seventh prior art uses a liquid lubricant for lubricating a bearing and for cooling the core portion of the spindle or the feed screw shaft. On the other hand, according to the invention, the liquid coolant and the liquid lubricant are independently supplied to the spindle or the screw shaft and the bearing to optimize the cooling of the spindle and the lubrication of the bearing.